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D A Halvorson

Publications and source records attributed to D A Halvorson.

At least 19 recordsLinked to original sources
PubMed2004

Evidence of avian pneumovirus spread beyond Minnesota among wild and domestic birds in central North America.

To detect avian pneumovirus (APV) in central North America, nasal turbinates or choanal deft tissues from domestic turkeys and wild birds were examined for the presence of APV RNA by reverse transcriptase-polymerase chain reaction (RT-PCR), whereas serum samples from domestic turkeys were analyzed for APV antibodies by enzyme-linked immunosorbent assay (ELISA). In 2002, the seroprevalence of disease in domestic turkeys in Minnesota remained high (42.3% of the flocks). In addition, there is evidence the disease has spread to turkey flocks in North Dakota (8.2%), South Dakota (7%), Iowa (10%), and Wisconsin (8.6%) as detected by RT-PCR and/or ELISA. House sparrows and ring-billed gulls sampled in Minnesota and snow geese from Saskatchewan, Canada, were found to harbor APV RNA. Sequence analysis of wild bird APV strains showed high amino acid sequence identity among wild bird isolates (<97%) and between wild bird and turkey viral isolates (93.2%-99.3%). This study demonstrated that APV infections were present in domestic turkey flocks and wild birds outside the state of Minnesota; however, the role of wild birds in spreading APV to domestic turkeys remains unclear.

Amino Acid Sequence↗
PubMed2002

Pathogenesis of avian pneumovirus infection in turkeys.

Avian pneumovirus (APV) is the cause of a respiratory disease of turkeys characterized by coughing, ocular and nasal discharge, and swelling of the infraorbital sinuses. Sixty turkey poults were reared in isolation conditions. At 3 weeks of age, serum samples were collected and determined to be free of antibodies against APV, avian influenza, hemorrhagic enteritis, Newcastle disease, Mycoplasma gallisepticum, Mycoplasma synoviae, Mycoplasma meleagridis, Ornithobacterium rhinotracheale, and Bordetella avium. When the poults were 4 weeks old, they were inoculated with cell culture-propagated APV (APV/Minnesota/turkey/2a/97) via the conjunctival spaces and nostrils. After inoculation, four poults were euthanatized every 2 days for 14 days, and blood, swabs, and tissues were collected. Clinical signs consisting of nasal discharge, swelling of the infraorbital sinuses, and frothy ocular discharge were evident by 2 days postinoculation (PI) and persisted until day 12 PI. Mild inflammation of the mucosa of the nasal turbinates and infraorbital sinuses was present between days 2 and 10 PI. Mild inflammatory changes were seen in tracheas of poults euthanatized between days 4 and 10 PI. Antibody to APV was detected by day 7 PI. The virus was detected in tissue preparations and swabs of nasal turbinates and infraorbital sinuses by reverse transcription polymerase chain reaction, virus isolation, and immunohistochemical staining methods between days 2 and 10 PI. Virus was detected in tracheal tissue and swabs between days 2 and 6 PI using the same methods. In this experiment, turkey poults inoculated with tissue culture-propagated APV developed clinical signs similar to those seen in field cases associated with infection with this virus.

Animals↗
PubMed2001

Immunohistochemical detection of avian pneumovirus in formalin-fixed tissues.

An immunohistochemical staining technique (IHC) was developed to detect avian pneumovirus (APV) antigen in formalin-fixed, paraffin-embedded tissue sections using streptavidin-biotin immunoperoxidase staining. Samples of nasal turbinates and infraorbital sinuses were collected from 4-week-old poults experimentally inoculated with APV and from older turkeys infected during naturally occurring outbreaks of avian pneumovirus. Tissue was fixed in 10% buffered neutral formalin, embedded in paraffin, sectioned and stained. Inflammatory changes were observed microscopically in the mucosa and submucosa of the nasal turbinates and infraorbital sinuses of both experimentally inoculated poults and naturally infected birds. Viral antigen was detected by IHC in the ciliated epithelial cells of nasal turbinates and infraorbital sinuses.

Animals↗
PubMed2001

Susceptibility of ducks to avian pneumovirus of turkey origin.

OBJECTIVE: To determine the susceptibility of ducks to avian pneumovirus (APV) of turkey origin. ANIMALS: 30 Pekin ducks that were 2 weeks old. PROCEDURE: Ducks were assigned to 3 groups (10 ducks/group). Ducks of groups 1 and 2 were inoculated (day 0) with 200 microl of cell-culture fluid containing APV of turkey origin (10(5.5) median tissue-culture infective dose/ml) by the oculonasal (group 1) or oral (group 2) route. Ducks of group 3 served as noninoculated control birds. Two ducks from each group were euthanatized 3, 6, 9, 15, and 21 days after inoculation. Blood samples, tissue samples from the lungs, trachea, nasal turbinates, duodenum, diverticulum vitellinum (Meckel's diverticulum), and cecum, and swab specimens from the choana, cloaca, and trachea were obtained from all birds during necropsy and examined for APV by use of reverse transcriptase-polymerase chain reaction (RT-PCR), virus isolation, and histologic examination. Blood samples also were examined for APV antibodies, using an ELISA. RESULTS: Tissue samples obtained up to 21 days after inoculation had positive results when tested by use of RT-PCR. Virus was isolated from nasal turbinates of birds inoculated via the oculonasal route. Serum samples obtained 15 and 21 days after inoculation had positive results when tested for APV-specific antibody. Clinical signs of disease were not observed in ducks inoculated with APV of turkey origin. CONCLUSIONS AND CLINICAL RELEVANCE: Ducks inoculated with APV of turkey origin may not develop clinical signs of disease, but they are suspected to play a role as nonclinical carriers of APV.

Animals↗
PubMed2000

Specific detection of avian pneumovirus (APV) US isolates by RT-PCR.

This report details the development of an RT-PCR assay for the specific detection of US isolates of avian pneumovirus (APV). Of the several primer pairs tested, two sets of primers derived from the matrix gene of APV were able to specifically detect the viral RNA of APV. The nucleotide sequence comparison of the PCR products of APV isolates from Minnesota suggested that these viruses were closely related to the Colorado strain of APV, but were distinct from subtypes A and B European isolates of turkey APV (turkey rhinotracheitis: TRT). This M gene-based PCR was found to be very specific and sensitive. APV as low as 8 x 10(-5) TCID50 (0.0323 microg/ml) could be detected using this assay. In addition, the two primers were able to differentiate isolates from turkeys in Minnesota.

Animals↗
PubMed2000

Pathogenic role of SEF14, SEF17, and SEF21 fimbriae in Salmonella enterica serovar enteritidis infection of chickens.

Very little is known about the contribution of surface appendages of Salmonella enterica serovar Enteritidis to pathogenesis in chickens. This study was designed to clarify the role of SEF14, SEF17, and SEF21 fimbriae in serovar Enteritidis pathogenesis. Stable, single, defined sefA (SEF14), agfA (SEF17), and fimA (SEF21) insertionally inactivated fimbrial gene mutants of serovar Enteritidis were constructed. All mutant strains invaded Caco-2 and HT-29 enterocytes at levels similar to that of the wild type. Both mutant and wild-type strains were ingested equally well by chicken macrophage cell lines HD11 and MQ-NCSU. There were no significant differences in the abilities of these strains to colonize chicken ceca. The SEF14(-) strain was isolated in lower numbers from the livers of infected chickens and was cleared from the spleens faster than other strains. No significant differences in fecal shedding of these strains were observed.

Animals↗
PubMed2000

Development of a highly sensitive and specific enzyme-linked immunosorbent assay based on recombinant matrix protein for detection of avian pneumovirus antibodies.

The matrix (M) protein of avian pneumovirus (APV) was evaluated for its antigenicity and reliability in an enzyme-linked immunosorbent assay (ELISA) for diagnosis of APV infection, a newly emergent disease of turkeys in United States. Sera from APV-infected turkeys consistently contained antibodies to a 30-kDa protein (M protein). An ELISA based on recombinant M protein generated in Escherichia coli was compared with the routine APV ELISA that utilizes inactivated virus as antigen. Of 34 experimentally infected turkeys, 33 (97.1%) were positive by M protein ELISA whereas only 18 (52.9%) were positive by routine APV ELISA 28 days after infection. None of the serum samples from 41 uninfected experimental turkeys were positive by M protein ELISA. Of 184 field sera from turkey flocks suspected of having APV infection, 133 (72.3%) were positive by M protein ELISA whereas only 99 (53.8%) were positive by routine APV ELISA. Twelve serum samples, which were negative by M protein ELISA but positive by routine APV ELISA, were not reactive with either recombinant M protein or denatured purified APV proteins by Western analysis. This indicates that the samples had given false-positive results by routine APV ELISA. The M protein ELISA was over six times more sensitive than virus isolation (11.5%) in detecting infections from samples obtained from birds showing clinical signs of APV infection. Taken together, these results show that ELISA based on recombinant M protein is a highly sensitive and specific test for detecting antibodies to APV.

Animals↗
PubMed2000

Avian pneumovirus (APV) RNA from wild and sentinel birds in the United States has genetic homology with RNA from APV isolates from domestic turkeys.

Nasal turbinates or swabs were collected from wild ducks, geese, owls, sparrows, swallows, and starlings and from sentinel ducks placed next to turkey farms experiencing avian pneumovirus (APV) infections and were analyzed for APV genome and infectious particles. APV RNA was detected in samples examined from geese, sparrows, and starlings. APV RNA and antibodies were also detected in two different groups of sentinel ducks. Infectious APV was recovered from sentinel duck samples. The APV M gene isolated from the wild birds had over 96% predicted amino acid identity with APV/Minnesota 2A, which was isolated earlier from domestic turkeys showing respiratory illness, suggesting that wild birds may be involved in spreading APV infection.

Amino Acid Sequence↗
PubMed2000

Isolation of avian pneumovirus from an outbreak of respiratory illness in Minnesota turkeys.

Antibodies to avian pneumovirus (APV) were first detected in Minnesota turkeys in 1997. Virus isolation was attempted on 32 samples (28 tracheal swabs, 4 pools of trachea and turbinates) that were positive for APV by reverse transcriptase polymerase chain reaction (RT-PCR). The cell cultures used were chicken embryo fibroblast (CEF), Vero cells, and QT-35 cells. Five virus isolates were obtained from these samples, and the identity of the isolates was confirmed by RT-PCR. Four isolates were obtained by inoculation of CEF cells, and 1 isolate was obtained in QT-35 cells after 3-7 blind passages in cell cultures. Vero cells did not yield any isolate on primary isolation; however, all 5 isolates could be adapted to grow in Vero cells following primary isolation in CEF or QT-35 cells. This is the first report of isolation of APV in Minnesota and also the first report of primary isolation of APV in QT-35 cells.

Animals↗
PubMed2000

A modified enzyme-linked immunosorbent assay for the detection of avian pneumovirus antibodies.

Avian pneumovirus (APV) infection of turkeys in Minnesota was first confirmed in March 1997. Serum samples (n = 5,194) from 539 submissions to Minnesota Veterinary Diagnostic Laboratory were tested by a modified enzyme-linked immunosorbent assay (ELISA). Of these, 2,528 (48.7%) samples from 269 submissions were positive and 2,666 (51.3%) samples from 270 submissions were negative for APV antibodies. Most positive samples were from Kandiyohi, Stearns, Morrison, and Meeker counties in Minnesota. In addition, 10 samples from South Dakota were positive. The sensitivity and specificity of the ELISA test with anti-chicken and anti-turkey conjugates were compared by testing field and experimental sera. The ELISA test with anti-turkey conjugate was more sensitive than that with anti-chicken conjugate. The ELISA tests with antigens prepared with APV strains isolated from Colorado and Minnesota were also compared. No difference was detectable. Currently, the Minnesota Veterinary Diagnostic Laboratory uses an antigen prepared from the Colorado isolate of APV and a goat anti-turkey conjugate in the ELISA test.

Animals↗
PubMed2000

Multidrug-resistant Salmonella Typhimurium DT104 in poultry.

Salmonella Typhimurium isolates from feed ingredients or poultry sources isolated during 1995 to 1997 from different geographical locations within Minnesota were examined for the presence of Salmonella Typhimurium definitive type 104 (DT104). Antibiotic susceptibility studies indicated that 15 of 50 isolates of Salmonella Typhimurium had an antibiotic resistance pattern (ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline) that is usually observed with multidrug-resistant Salmonella Typhimurium DT104. Of the 15 isolates showing the antibiotic resistance pattern, 8 isolates were phage type 104, 3 isolates were typed as phage type 104 complex, and the remaining 4 isolates belonged to phage types 193, 81, and 126. DT104 was recovered from both feed ingredients and poultry samples. Of the seven feed ingredient-associated Salmonella Typhimurium isolates, four were DT104, whereas only 7 of 43 poultry-associated Salmonella Typhimurium isolates were DT104. A repetitive sequence-based polymerase chain reaction (rep-PCR) of 50 isolates of Salmonella Typhimurium representing 13 phage types identified seven distinct fingerprint profiles. No correlation between phage type and rep-PCR type was noticed. Eleven Salmonella Typhimurium isolates belonging to DT104 and its complex were grouped into two closely related rep-PCR types.

Animals↗
PubMed1999

A rapid strip immunoblot assay for the specific detection of Salmonella enteritidis infection in chickens.

A rapid strip immunoblot assay (RSIA) was developed using recombinant SEF14 antigen. The rSEF14-RSIA was very specific in detecting antibodies to Salmonella enteritidis in chickens. When serum samples obtained from groups of chickens (N = 5) inoculated with six different Salmonella serovars were tested in rSEF14-RSIA, only serum samples obtained from S. enteritidis inoculated birds reacted with rSEF14 antigen except for a group of chickens that had been inoculated with S. dublin. To assess the sensitivity of the rSEF14-RSIA, groups of chickens were inoculated with either 10(4) cfu or 10(10) cfu of S. enteritidis and the serum and egg yolk were analyzed for SEF14 antibodies. By 1 week after infection 66-78% of chickens were found positive for SEF14 antibodies in the serum and the number of positive birds increased subsequently to 89-100%. The S. enteritidis specific antibodies appeared as early as 6 days after infection in the egg yolk of infected chickens. The antibodies to SEF14 in both the serum and egg yolk persisted for at least 7 weeks after infection in a significant proportion of chickens. Our results suggest that rSEF14-RSIA can be a practical and efficient screening test for identifying S. enteritidis infected chickens.

Animals↗
PubMed1998

Application of recombinant fimbrial protein for the specific detection of Salmonella enteritidis infection in poultry.

A number of disease outbreaks of Salmonella enterica serotype enteritidis (SE) in humans have been traced to the consumption of SE-contaminated egg and egg products. A rapid, specific, and inexpensive method of detecting SE infection in poultry is necessary to reduce human outbreaks. We evaluated rSEF14 fimbrial antigen of SE for specific detection of SE-infected birds in latex agglutination test and enzyme-linked immunosorbent assay. rSEF14 antigen was highly specific in identifying birds infected with SE. The sera from birds infected with closely related serogroup-D Salmonella and other avian pathogens did not react with rSEF14 antigen. The rSEF14 antigen identified antibodies in serum of 88% of birds during the first 2 weeks of infection, and 100% of the birds subsequently. The SE-specific antibodies were detected in egg yolk as early as 6 days post-infection in rSEF14-enzyme-linked immunosorbent assay. Our results suggest that rSEF14-based assays could be used as screening tests for detection of SE antibodies and would overcome the cross reactions observed with existing serological tests.

Amino Acid Sequence↗
PubMed1997

Market turkey performance, air quality, and energy consumption affected by partial slotted flooring.

Two experiments were conducted with 600 male Large White turkeys to examine performance and health when reared from 5 to 18 wk of age on litter (L) partially slotted flooring (SF), and under two ventilation rates-control and reduced ventilation (80% control). In both experiments, body weights were improved significantly (P < 0.05) for turkeys reared on SF compared to L by 11 and 16% in Experiments 1 and 2, respectively. In comparison to L, SF significantly decreased incidence of leg problems in Experiment 1, whereas the incidence of breast blisters and buttons were increased in Experiment 2. Ammonia levels were reduced with SF, whereas dust levels were increased. Ventilation rate did not affect turkey performance. Ammonia and carbon dioxide levels were increased with reduced ventilation in Experiment 1. Dust levels were not affected by ventilation rate. Supplemental energy use was decreased in the SF system or by reducing the ventilation rate. In comparison to the control ventilation/litter treatment, the greatest decrease in energy use was observed with SF at 80% ventilation rates. Results indicate that the use of SF in a cold climate can improve body weight and substantially reduce energy use when excessive litter moisture is a problem. However, a greater incidence of blisters will limit application of SF due to lowered carcass quality and value.

Air↗
PubMed1996

A dot immunobinding assay (dot-ELISA) for the rapid serodiagnosis of Salmonella enteritidis infection in chickens.

A dot immunobinding assay (DIA) was developed for the detection of antibodies to Salmonella enteritidis. Western blot analysis of outer membrane proteins from SE identified 2 polypeptides of molecular masses 43 and 46 kD that were specific for S. enteritidis. These 2 polypeptides were utilized as antigens in the DIA. The DIA was tested on sera from chickens experimentally infected with S. enteritidis. Results of the DIA were compared with that of conventional microagglutination and serum plate tests. The DIA was a highly specific and sensitive test that can be useful for screening birds to determine if they are infected with S. enteritidis. Its simplicity, reliability, reproducibility, and speed in interpreting the assay results makes it a useful screening test for flock monitoring.

Animals↗
PubMed1996

Salmonella enteritidis in eggs, cloacal swab specimens, and internal organs of experimentally infected White Leghorn chickens.

OBJECTIVE: To investigate prevalence of Salmonella enteritidis-positive eggs, excretion of the organism in fecal droppings, and infection of internal organs after oral inoculation of White Leghorn hens with S enteritidis phage type 8. ANIMALS: 30 White Leghorn laying hens. PROCEDURE: At 25 weeks of age, hens were each inoculated orally with 10(10) colony-forming units of S enteritidis, then were observed for 8 weeks. RESULTS: Salmonella enteritidis Y-BP2 did not cause any clinical signs of disease or decrease in egg production. However, at 1 week after inoculation, 63.9% of the eggs collected from inoculated hens were culture positive for S enteritidis. The organism was isolated from the shell washings, egg shells, yolk, and albumen. A total of 592 eggs from S enteritidis-inoculated hens were examined. Of these eggs, 157 (26.5%) were positive for S enteritidis on external shell washings alone, 17 (2.9%) were positive for S enteritidis internally, and 44 (7.4%) were positive for S enteritidis externally and internally. The percentage of culture-positive eggs gradually decreased between postinoculation weeks 2 and 5, then gradually increased to a high of 76% at week B. At 3, 7, and 10 days after S enteritidis inoculation, cloacal swab specimens from 3 hens were positive for S enteritidis. Salmonella enteritidis was recovered from ovary, oviduct, liver, and cecal junction from S enteritidis-inoculated hens. CONCLUSIONS: Our results indicated that birds infected with this isolate produced S enteritidis-positive eggs at high frequencies initially, that decreased over time. When S enteritidis antibody began to decrease, reaching geometric mean titer < or = 40, the frequency of S enteritidis-positive eggs increased.

Analysis of Variance↗